Estimating parameters in a state space model

Dear Matlab users,

Given the code below, I want to estimate "A" from the observations "y" using the system identification toolbox. Can somebody help me? I have tried ssest(y,1), but with very poor results.

A = 0.4;
N = 1000;
x = zeros(N,1);
y = zeros(N,1);
v = randn(N,1)*1e-1;
e = randn(N,1)*1e-1;
for i = 1:N
    x(i+1) = A*x(i) + v(i);
    y(i) = x(i) + e(i);
end